The present invention relates to carbonyl iron powder, herein also referred to as CIP for convenience. More specifically, this invention relates to a method for protecting CIP from extensive atmospheric oxidation and to compositions prepared with the protected CIP.
CIP is used as a component in the formation of cores in electronic devices such as tuned circuits, chokes and transformers. Typically, CIP is processed so that its individual particles are insulated and then intimately mixed with a binder and the magnetic core is thereafter molded from the mixture, using conventional molding methods. The resulting cores can be lightly machined and turned if necessary. Examples of suitable insulating materials include lacquers, shellacs, waterglass and phosphoric acid. Examples of suitable binders include thermosetting resins and thermoplastic resins. The volume fraction of iron in the core can be as high as 95%.
When CIP is mixed with a silicone binder it is not readily accepted by the binder. In addition the resulting composition undergoes oxidation in the presence of atmospheric moisture.